MEDAL CUTTING ENGINE.

Sir, I herewith forward drawings and description of an apparatus which I have eontrived for forming medallions in the fathe, which I shall be gratified by your inserting in your valuable Journal.

I am, respectfully yours,

N. S. HEINEKEN. Sidmouth, Devon, May 30, 1836.

Description of the Engravings.

Fig. 1 is a ground plan; fig. 2, a section; and fig. 3, a front elevation of the machine. aaa, the mandril of the lathe, with a chuck screwed upon it containing the substance upon which the medal is to be formed; B, the poppet of the lathe.

66

inches

CC, two carriages" screwed to the poppet, in which revolve the spindles D and E.. The spindle D has fixed to it at one end the wheel F, which is 2 in diameter, and has 80 teeth; on the other end is screwed the chuck G, in which is fixed the medal to be copied. The spindle E has also at one end a wheel H of 120 teeth, and 4 inches diameter; and at the other end a wheel I, bevelled at an angle of 45°, having 28 teeth, and being 1 inch diameter at the largest part.

K is a wheel fixed to the mandril of the lathe, of exactly the same size and number of teeth as the wheel F.

L is a stud affixed to the poppet, which carries a wheel of 40 teeth, and is 1% inch diameter. This wheel runs in geer with the two wheels F and K, and underneath them, as shown in the front view.

M is a bevelled wheel of 108 teeth, and 2,7 inch diameter at the largest part. This wheel is fixed upon the screw O of the slide rest NN, which screw has 50 threads in the inch.

P is a dovetailed plate-as usual, sliding at right angles to the foundation of the rest N N. To this plate is screwed at right angles another plate QQQ, having its two ends formed into male dovetails, as shown in the section. Upon these dovetails slide the receptacles" RR, containing the small "rubber" wheel W and the chisel x. SS is a screw, passing through the centre of the plate P, one end of which screw is received by a stud T, fixed in the plate of the rest, which slides upon the top or foundation N N.

V is a slight brass-wire spiral spring, pressing against the milled head of the

screw SS and the sliding-plate P, the conséquence of which is, that the rubberwheel and tool, attached to this plate by the plate QQ, are kept in contact, the one with the medal, and the other with the substance to be cut; and the pressuré may be increased or diminished by turning the milled head of the screw S S.

a, the screw by which the plate QQ is affixed to the sliding-plate P.

bbb, three small screws, the ends of which press on the plate P, and allow of adjusting the rubber W and tool x in a line with the centres of the medal to be copied and the substance to be cut.

cc, two screws, which press upon the tool x, and, as this rests upon the plate QQ, fasten at the same time the tool and its receptacle.

dd are two similar screws for fixing the rubber-wheel. ef, two square-headed screws, which adjust the receptacles RR with the tool and rubber to the centre of the medal and work.

gh, two similar screws, which press against the ends of the tool x and rubber W, in order to adjust them accurately to touch the medal and work.

Mode of Operation.

This will be evident from inspection of the drawings, (which, I may state, are ths of the full size). The medal being fixed true in the chuck G, and the substance to be operated upon on the chuck Y, the rubber-wheel and tool are brought to the centres of their work, and adjusted so as to touch it. Now the wheel K upon the mandril of the lathe aa gives motion to the small wheel on the stud L; this again puts in motion the wheel F, and the medal on G and the work on Y revolve in the same direction, and in every respect similarly. The copy of the medal will, therefore, be like the original. But if it should be desired to reverse the copy, this is effected by taking away the stud-wheel L, and allowing the wheels K and F to run in geer together. Again, the wheel K gives motion to the wheel H, and consequently to the pinion T. This again I puts in motion the wheel M, which, turning round the screw O, causes the rubber W and the tool x to be drawn across the medal and the work. The spiral spring V acting upon the sliding-plate P, and allows the rubber W to follow the elevations and depressions of the medal, and the tool, consequently, to carve out the

copy. But could points be substituted, it would be an improvement. These, however, I have found to be so rapidly worn away, as to be useless. If some of the fine Berlin castings in iron were used as patterns, they would be little injured by employing hard points or steel rubbers, and the copies would be proportionably better. I may state, that when a medal in high relief is to be copied, it may be necessary to have a stop-screw attached to the sliding-plate P, to limit the cutting of the tool. And in forming any medallion the work must be passed over and over again until it is perfected, a slow-hand motion being used for the lathe, and the least pressure being given by the spring V. The operation may be expedited by having the nut, in which the traversing screw of the slide-rest (0)

+447

works, slit so that the screw might be at once relieved, and the tool, &c. set back by hand to the centre of the work, instead of having to set them back by the reversed motion of the lathe, &c. The medals would also be better executed if either the screw O were finer, or if the diameters of the wheels H and M were increased, as the strokes left by the cutting of the tool would be then so fine as to be imperceptible. This, however, I did not foresee when I constructed the engine. By a little alteration, I doubt not but that this same apparatus might be made to copy small busts, ornamented vases, &c. they being affixed to the spindle D, and the slide-rest, &c. turned at right angles to its present position. N. S. HEINEKEN.

the earth's axis is constant, without any sensible variation. Hence an exact rotation of the earth is performed between

culmination and culmination of a fixed

star.

The acceleration or retardation of the earth in its annual orbit, as the distance from the sun is diminished or increased, is no preventive to the equableness of the astro-terrestrial period, the unvarying duration whereof has the confirmation of nightly and daily chronometrical ascer tainment.

As the diurnal equation of time has, therefore, no relation to the side ial revolution; neither also is the recession of the equinoxes referable to any motion of the earth or fixed stars, for this recession must be gradual throughout the year. But we have concluded against any reservation, ecliptical or other, in the abso luteness of the earth's parallelism in rotation on its axis.

Yet as the fact of the recession is undisputed, its proper origin remains to be considered. And here there can be no dilemma, as the only inference remaining is, that the position of the sun itself must alter in the requisite lateral quantity; that besides that luminary's verticity on its axis, the solar centie moves around the centre of the system (near the exterior of the orb of light) in about 25,920 of our years.

This revolution may be necessary as a counterbalance to the vacillation that the planets, from the changes in their situations, might occasion to the sun; which, though possessing gravity (or intensity of progress through heaven's firmament) vastly superior to an equipoise of all the worlds which circumvolve it in their courses, would else, or less or more, according to the planet's eloinations or approximations, be correspondingly disturbed (unless they for an instant neutralised their influences on the central mass, in opposition checking each other.

Regularity is so conspicuous throughout the dependent parts, that the ascription of a perfect motion to the governing primary of the system, instead of a perpetually shifting agitation, may require small apology, especially as the analogy of gravity and projectile motion concurs with observations in affording ground for the probability of its deduction.

However, this hypothesis of a planetary orbit to the sun is not essential to the main proposition, as our globe's relation to the fixed stars is independent of ecliptical mutation; for it is as impossible for

An observation of what stars are in the meridian being made instantly with ascertaining what is the position of the index in its circuit, the vessel (provided with a celestial globe or planisphere) may set sail; and its departure from that longitude is detected to be east, by the apparent slowness of the time-keeper in comparison with the stars' advance-and by the seeming delay of stars coming to meridian after the port-time assigned them, the ship's departure is to the west; the difference of longitude in either case being equivalent, in degrees, minutes, seconds, thirds, &c. of the parallel of latitude, to the arc between the port-position of the index when the stars now on this meridian are on that, and its present pointing.